Some polymeric particulates may deform over time when exposed to stress and temperature conditions experienced during shipment. Additionally, the surfaces of polymeric particulates in contact with each other can sinter together at the interface thereby creating a bond. The combined effect of deformation and bonding at the contact points makes the polymeric particulates mass appear blocky.
Blockiness refers to the lumpy appearance of polymeric particulates in bags, boxes or railcars. In worst situation, the entire mass of the polymeric particulates may become a single lump or a block (hence called massing). This can be contrasted with polymeric particulates, where the polymeric particulates remain free-flowing regardless of stress, temperature and time history during shipment.
The blocking or massing of polymeric particulates creates a significant problem for end users. Blocky polymeric particulates are difficult to handle, and are especially problematic during blending, metering and feeding into extruders. The blocking problem applies to a wide variety of ethylene-alpha olefin copolymers, ethylene-propylene copolymers, EPDM, and EVA polymers.
Similarly, low molecular weight fraction component can migrate to the surface of a particle in low-crystalline polyolefins causing stickiness or tackiness. This results in significant problems during subsequent handling and processing in post-pelletization process.
Despite the research efforts in improving blockiness or stickiness in the past, there is still a need for a coated polymeric particulates having improved blocking and stickiness properties, and there is also a need for a coating process for polymeric particulates having improved blocking and stickiness properties.